1. Field of the Invention
The present invention concerns a superconductor manufacturing process.
2. Description of the prior art
It is known from French Pat. No. FR-A- 2 165 660 to fabricate superconductors from a multifilament strand of an alloy of niobium and tin, obtained by diffusing tin from a bronze matrix into a strand of niobium filaments at a temperature of approximately 800 degrees C., and to electrically insulate the superconductive strand by means of carbon or magnesium oxide, which have the property of not being soluble in the metals during the heat treatment in question. In the prior art process, as described in the patent on page 4, line 28, the multifilament strand, at its final diameter, is passed into a bath of magnesium hydroxide immediately prior to the diffusion heat treatment. It follows that the superconductive materials are treated when they are of small diameter and very great length.
The disadvantage of this process resides in the fact that it is necessary to apply the insulation over a very great length of wire. This can be accomplished only be spooling the superconductive strand and then paying it out (page 5, line 3), only to subsequently rewind it in order to construct an electromagnet. It should be noted that niobium-tin (Nb.sub.3 Sn) superconductors are brittle once diffusion has been carried out and that the paying out and rewinding are difficult to execute without causing breaks, as a result of which the superconductors cannot function.
The process in accordance with the present invention remedies this disadvantage. In this process, the electrical insulation is applied before the strand is drawn to final length, which facilitates its manufacture and renders it reliable.